Anal Examination Under Anesthesia with Abscess Drainage and Evaluation for Fistula

Anorectal abscesses most commonly result from obstruction of glandular crypts in the anorectal canal. Abscesses are commonly diagnosed by clinical exam with fluctuance, induration, and tenderness around the perianal tissue. Abscesses are managed with incision and drainage. For superficial perianal abscesses bedside lancing can be performed, but for more complex or ischiorectal or postanal abscess, examination under anesthesia in the operating room is preferred. Complete evacuation of the abscess with breakdown of loculated abscess pockets is critical to fully control the infection. Drains may also be left in a deep abscess pocket to prevent the skin prematurely closing before the cavity has healed. Imaging is selectively performed with CT or MRI to identify occult infections or further identify proximal extent of abscess cavity or associated fistula. For recurrent abscesses, associated fistula tracts should also be identified and, if possible, treated intraoperatively. Antibiotics are utilized for patients with cellulitis or those who are immunosuppressed. We present an adult male with recurrent anorectal abscesses with a new anterior abscess collection, which was managed with anal exam under anesthesia with incision and drainage of abscess collection and drain placement. 

Anorectal abscesses form due to obstruction of glandular crypts in the anorectal canal.^1-3 Anal glands empty into ducts oriented transversely to the internal sphincter and drain into anal crypts at the dentate line.^1,3 Obstruction of these ducts and crypts promote infection and abscess formation along perianal and perirectal planes. Common pathogens include: Bacteroides fragilis, Peptostreptococcus, Prevotella, Fusobacterium, Porphyromonas, Clostridium, Staph aureus. Streptococcus, and E. coli.³ 

Clinically, it is important to describe anorectal abscesses by the anatomic space in which they develop, most commonly perianal and ischiorectal. Additional spaces include intersphincteric, supralevator, submucosal, and postanal spaces.¹ The location of the abscess within these spaces will determine whether drainage may be performed internally into the rectal canal, or externally through skin. While the exact percentage ranges from 30–70%, many anorectal abscesses have an associated anal fistula.¹ Anorectal abscesses are more common in males with a peak incidence in young-mid adulthood, ages 20–40.¹ 

A male in his 60s with an unremarkable past medical history status post posterior anal abscess drainage with seton placement (x2) one year prior presented with worsening rectal pain. The patient denied bleeding per rectum, changes in bowel movements, or increased pain with defecation.

Physical exam should include a rectal exam to evaluate for fluctuance, induration, tenderness to palpation, and erythema in the perianal area.¹ Cellulitis or gross evidence of fistula tracts should also be noted. If the abscess is spontaneously draining, blood or purulent fluid may be appreciated on exam. The depth of the abscess collection can also be evaluated grossly. Superficial abscesses are more likely to drain spontaneously and present without fever in comparison to deeper abscesses. Imaging is not required prior to drainage of an abscess collection. However, ultrasound and MRI may aid in localizing complex abscesses and associated fistulae.¹ 

This patient presented with a right anterior abscess on scrotum with a punctate area of draining pus. 

The first line management of an anorectal abscess is incision and drainage.¹ Drainage should include interrogation of the wound for any loculated collections that should be subsequently broken down to ensure comprehensive drainage. The skin incision should also be large enough to prevent early closure of the wound and reaccumulation of the abscess. A counter incision may also be necessary to promote drainage and relieve skin tension. Finally, a drain may also be placed to promote drainage.¹

Fistula tracts may be identified intraoperatively by injecting H₂O₂ into the abscess pocket and evaluating for bubbles inside the anorectal canal. In cases of first time abscess drainage, it is unnecessary to look for evidence of fistula. However, if simple fistulas are identified with minimal sphincter involvement, then fistulotomy at the time of the primary incision and drainage is performed to reduce the risk of persistent abscess, recurrence, and need for repeat surgery.^1,2 In the case presented, we looked for communication of the abscess with prior fistulotomy sites.

The rate of recurrence of anorectal abscess after incision and drainage is approximately 44% in one year.¹ Additional complications from these procedures include fistula formation and fecal incontinence.²

Most patients will not require antibiotics at the time of discharge. However, patients with cellulitis and/or systemic signs of infection or underlying immunosuppression benefit from postprocedural antibiotics.³ Aerobic and anaerobic organisms should be appropriately covered.³ Sitz baths are recommended for all patients postoperatively. 

Patients with anorectal abscesses should also be evaluated for additional signs of Crohn’s disease including surgical scars, anorectal deformities, or external fistula openings, and colonoscopy aids in this evaluation to rule out chronic bowel disease.^1,3 

An adult male with a history of anorectal abscesses presents with anterior perirectal pain and fluid collection with purulent drainage. Patient underwent incision and drainage of abscess collection with Pezzer drain placement to promote complete drainage of abscess collection.

Drain (Pezzer or Malecot).

Nothing to disclose.

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